Ink jet printer

ABSTRACT

The present invention relates to an ink jet printer provided with a line type ink jet head formed by a plurality of ink jet heads, in which a plurality of ink jet heads are fixed to a plate, and an ink is injected to an ink injected subject from a plurality of ink jet heads in a state in which a plate surface of the plate and the ink injected subject are faced to each other.

TECHNICAL FIELD

The present invention relates to an ink jet printer.

BACKGROUND ART

An ink jet printer executes a print to a subject to be printed byinjecting ink to a subject to be injected the ink from an ink jet head.As specific aspects thereof, a “direct print” which executes the printto a paper by injecting the ink to the paper from the ink jet head, andan “indirect print” which executes the print to the paper by injectingthe ink to an intermediate transcription body from the ink jet head andtranscribing the ink to the paper from the intermediate transcriptionbody are given as examples.

A normal ink jet printer executes the print to a paper by relative movean ink jet head and the paper (or an intermediate transcription body orthe like) in two directions so as to scan the paper (or the intermediatetranscription body or the like) with respect to the ink jet head or scanthe ink jet head with respect to the paper (or the intermediatetranscription body or the like). This is because in the normal ink jetprinter, a printing width of the ink jet head is smaller than a printingwidth of the paper with respect to both of a vertical direction and ahorizontal direction of the paper.

On the contrary, a line type ink jet printer executes a print to a paperby relative move an ink jet head and the paper (or an intermediatetranscription body or the like) in one direction so as to scan the paper(or the intermediate transcription body or the like) with respect to theink jet head or scan the ink jet head with respect to the paper (or theintermediate transcription body or the like). This is because in theline type ink jet printer, the printing width of the ink jet head issmaller than the printing width of the paper with respect to only onedirection of the vertical direction and the horizontal direction of thepaper. In other words, since the printing width of the ink jet head isequal to or more than the printing width of the paper with respect tothe other direction, it is not necessary to relatively move the ink jethead and the paper (or the intermediate transcription body or the like)in two directions. The line type ink jet printer is desired to come intopractical use in view of a high-speed printing.

An ink jet head of the line type ink jet printer is called as a linetype ink jet head. As a method of forming the line type ink jet head,there can be considered a method of forming one line type ink jet headfrom one long ink jet head. In the case of employing this method, sinceit is necessary to manufacture a very long ink jet head, there areproblems in a work size of the manufacturing apparatus, and a yieldratio at a time of manufacturing. However, since there is no effectivecountermeasure against these problems at the present time, it is hard toemploy this method for the time being.

Accordingly, as a method of forming the line type ink jet head, therecan be considered a method of forming one line type ink jet head from aplurality of short ink jet heads. In the case of employing this method,since it is necessary to integrally form the short ink jet heads witheach other, there is a problem how the line type ink jet head isdesigned. There is a possibility that a disadvantage is generated at atime of manufacturing the line type ink jet head and maintaining theline type ink jet head, in accordance with the design.

DISCLOSURE OF THE INVENTION

An object of the present invention (a first invention) is to achieve anink jet printer provided with a line type ink jet head formed from aplurality of ink jet heads, in which an excellent design is provided.

The invention (the first invention) relates to the ink jet printerprovided with a line type ink jet head formed from a plurality of inkjet heads, wherein a plurality of ink jet heads are fixed to a plate,and an ink is injected to an ink injected subject from a plurality ofink jet heads in a state in which a plate surface of the plate and theink injected subject are faced to each other.

In accordance with the invention (the first invention), it is possibleto achieve an ink jet printer having an excellent design, wherein theink jet printer provided with the line type ink jet head formed by aplurality of ink jet heads.

For example, it is possible to make it easy to attach and detach the inkjet head and position the ink jet head at a time of manufacturing andmaintaining the line type ink jet head, by fixing a plurality of ink jetheads to the plate such that a plurality of ink jet heads pass throughthe plate. For example, it is possible to make the ink receiving subjectvertical to the injecting direction of the ink, by fixing a plurality ofink jet heads to the plate such that the ink injecting direction of aplurality of ink jet heads is parallel to the plate surface, therebymaking the ink receiving subject vertical to the ink injectingdirection. For example, it is possible to make the ink receiving subjectparallel to the injection surface of the ink, by fixing a plurality ofink jet heads to the plate such that the ink injection surface of aplurality of ink jet heads is parallel to the plate surface, therebymaking the ink receiving subject parallel to the plate surface. Asmentioned above, in accordance with the invention (the first invention),it is possible to achieve the ink jet printer having the excellentdesign.

An object of the invention (a second invention) is to achieve an ink jetprinter in which it is easy to attach and detach an ink jet head andposition the ink jet head at a time of manufacturing and maintaining theline type ink jet head, in connection with the first invention mentionedabove.

The invention (the second invention) relates to an ink jet printer asdescribed in the first invention mentioned above, wherein the ink jethead is fixed to the plate by an adjust plate.

In accordance with the invention (the second invention), in connectionwith the first invention mentioned above, it is possible to achieve theink jet printer in which it is easy to attach and detach the ink jethead and position the ink jet head at a time of manufacturing andmaintaining the line type ink jet head.

An object of the invention (a third invention) is to achieve an ink jetprinter in which a tube for supplying the ink to the ink jet head and/ora cable for sending a signal to the ink jet head does not form anobstacle at a time of manufacturing and maintaining the line type inkjet head, in connection with the first invention mentioned above.

The invention (the third invention) relates to an ink jet printer asdescribed in the first invention mentioned above, wherein a tube forsupplying the ink to the ink jet head and/or a cable for sending asignal to the ink jet head is buried in the plate.

In accordance with the invention (the third invention), in connectionwith the first invention mentioned above, it is possible to achieve theink jet printer in which the tube for supplying the ink to the ink jethead and/or the cable for sending the signal to the ink jet head doesnot form the obstacle at a time of manufacturing and maintaining theline type ink jet head.

An object of the invention (a fourth invention) is to achieve an ink jetprinter in which it is easy to attach and detach the ink jet head andposition the ink jet head at a time of manufacturing and maintaining theline type ink jet head, in connection with the first invention mentionedabove.

The invention (the fourth invention) relates to an ink jet printer asdescribed in the first invention mentioned above, wherein tubes forsupplying the ink to the ink jet head and/or cables for sending a signalto the ink jet head are respectively connected by a connector.

In accordance with the invention (the fourth invention), in connectionwith the first invention mentioned above, it is possible to achieve theink jet printer in which it is easy to attach and detach the ink jethead and position the ink jet head at a time of manufacturing andmaintaining the line type ink jet head.

An object of the invention (a fifth invention) is to achieve an ink jetprinter in which an ink meniscus of an ink jet head is maintained in astable state even in the case that a movable plate is moved, inconnection with the first invention mentioned above.

The invention (the fifth invention) relates to an ink jet printer asdescribed in the first invention mentioned above, wherein an ink tankfor supplying the ink to the ink jet head is fixed to the plate, and aheight of an ink liquid surface in the ink tank is controlled such thatthe height of the ink liquid surface in the ink tank is maintained at aset value with respect to the movable plate.

In accordance with the invention (the fifth invention), in connectionwith the first invention mentioned above, it is possible to achieve theink jet printer in which the ink meniscus of the ink jet head ismaintained in the stable state even in the case that the movable plateis moved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an ink jet printer in accordance with an embodiment of theinvention, and specifically shows a state of the ink jet printer at atime of printing.

FIG. 2 shows an ink jet printer in accordance with the embodiment of theinvention, and specifically shows a state of the ink jet printer at atime of maintenance.

FIG. 3 is a view for explaining a line type ink jet head.

FIG. 4 is a view for explaining an adjust plate.

FIG. 5 is a view for explaining the adjust plate.

FIG. 6 is a view for explaining ink suction.

FIG. 7 is a view for explaining a maintenance unit.

FIG. 8 is a view for explaining a sub ink tank.

FIG. 9 is a view for explaining a liquid surface control.

FIG. 10 is a view for explaining a liquid surface control.

FIG. 11 shows a procedure of a liquid surface control with respect to asub ink tank.

FIG. 12 shows a procedure of a liquid surface control with respect to amain ink tank.

BEST MODE FOR CARRYING OUT THE INVENTION

A description will be given of an embodiment in accordance with thepresent invention with reference to the accompanying drawings.

FIGS. 1 and 2 show an ink jet printer 101 in accordance with anembodiment of the invention. Specifically, FIG. 1 shows a state of theink jet printer 101 at a time of printing, and FIG. 2 shows a state ofthe ink jet printer 101 at a time of maintenance.

(Ink Jet Printer 101)

The ink jet printer 101 is a line type ink jet printer, and is providedwith a line type ink jet head 102. The line type ink jet head 102 isprovided with a plurality of ink jet heads 111, a plate 112, adjustplates 113, ink tubes 114, signal cables 115, ink tube connectors 116,signal cable connectors 117, sub ink tanks 118 and ball screws 119.

The ink jet printer 101 injects ink to a paper 103 from the line typeink jet head 102 so as to execute a print to the paper 103. The ink jetprinter 101 injects the ink to the paper 103 from the line type ink jethead 102 in a state in which a vertical direction of the paper 103 is inparallel to a direction D1 and a horizontal direction of the paper is inparallel to a direction D2, as shown in FIG. 1.

A printing width of the line type ink jet head 102 is designed so as tobe smaller than a printing width of the paper 103 with respect to thevertical direction (the direction D1) of the paper 103, and to be equalto or larger than the printing width of the paper 103 with respect tothe horizontal direction (the direction D2) of the paper 103.Accordingly, the ink jet printer 101 executes the print to the paper 103by relative move the line type ink jet head 102 and the paper 103 in thedirection D1. The ink jet printer 101 in accordance with the presentembodiment executes the relative movement mentioned above by feeding thepaper 103 in the direction D1 in a state in which the line type ink jethead 102 is at a standstill.

(Line Type Ink Jet Head 102)

The line type ink jet head 102 is formed by a plurality of (three inthis case) ink jet heads 111. FIG. 3 is a view for explaining the linetype ink jet head 102. As shown in FIG. 3, each of the ink jet heads 111is provided with a nozzle line 122 in which a plurality of nozzles 121are arranged in a line such that a nozzle interval is fixed. In thepresent embodiment, the ink jet head 111 has a rectangularparallelepiped outer shape, and the nozzle line 122 is provided in aside surface of the ink jet head 111. The side surface corresponds aninjection surface of the ink, and a normal direction of the side surfacecorresponds to an injecting direction of the ink.

Each of the ink jet heads 111 is arranged such that the nozzle line 122is in parallel to the direction D2. A printing width of each of the inkjet heads 111 in the direction D2, that is, a width of the nozzle line122 in each of the ink jet heads 111 is smaller than the printing widthof the paper 103. A printing P1 in FIG. 1 is a printing obtained by oneink jet head 111.

However, the printing width of the line type ink jet head 102 in thedirection D2, that is, a total of the widths of the nozzle lines 122 inthe respective ink jet heads 111 becomes equal to or larger than theprinting width of the paper 103, by arranging the respective ink jetheads 111 such that the nozzle lines 122 are shifted to each other inthe direction D2. A printing P2 in FIG. 1 is a printing obtained by oneline type ink jet head 102. In this case, the respective ink jet heads111 are arranged such that the nozzle interval is fixed, that is, arelation P11=P12 and P21=P22 is established as shown in FIG. 3. Further,for convenience of driving each of the ink jet heads 111, the respectiveink jet heads 111 are arranged such that a relation P31=P32 isestablished.

(Ink Jet Head 111 and Plate 112)

As shown in FIG. 1, in the ink jet printer 101 in accordance with thepresent embodiment, a plurality of ink jet heads 111 are fixed to acommon plate 112. Accordingly, each of the ink jet heads 111 ismaintained in a state in which the ink jet head is positioned at thearrangement mentioned above. The plate 112 is formed in a flat outershape, and has a “plate surface” corresponding to a wide surface and an“end surface” corresponding to a narrow surface. In the presentembodiment, since the plate 112 is formed in a rectangularparallelepiped outer shape, the plate 112 has two “plate surfaces” andfour “end surfaces”.

Further, as shown in FIG. 1, the ink jet printer 101 in accordance withthe present embodiment is designed such that the print to the paper 103is executed by injecting the ink to the paper 103 from a plurality ofink jet heads 111 in a state in which the plate surface of the plate 112is faced to the paper 103. In this case, the plate surface of the plate112 and the paper 103 are faced such that the plate surface of the plate112 and the paper 103 are in parallel to each other. This design isemployed for the reason because it is possible to achieve the ink jetprinter 101 having an excellent design by employing the design mentionedabove.

For example, as shown in FIG. 1, it is possible to make it easy toattach and detach the ink jet head 111 and position the ink jet head 111at a time of manufacturing and maintaining the line type ink jet head102, by fixing a plurality of ink jet heads 111 to the plate 112 suchthat a plurality of ink jet heads 111 pass through the plate 112. Inthis case, the ink jet heads 111 pass through the plate 112 on the basisof an aspect that the ink injection surfaces of the ink jet heads 111make an intrusion into the plate surface in a side of the paper 103 fromthe plate surface in an opposite side to the paper 103.

Further, for example, as shown in FIG. 1, it is possible to make thepaper 103 vertical to the injecting direction of the ink, by fixing aplurality of ink jet heads 111 to the plate 112 such that the inkinjecting direction of a plurality of ink jet heads 111 is vertical tothe plate surface, thereby making the paper 103 parallel to the platesurface. In this case, the ink injecting direction of the ink jet heads111 is made vertical to the plate surface by fixing the rectangularparallelepiped ink jet heads 111 vertical to the plate surface.

Further, for example, it is possible to make the paper 103 parallel tothe injection surface of the ink, by fixing a plurality of ink jet heads111 to the plate 112 such that the ink injection surface of a pluralityof ink jet heads 111 is parallel to the plate surface, thereby makingthe paper 103 parallel to the plate surface. In this case, the inkinjection surface of the ink jet heads 111 is made parallel to the platesurface by fixing the rectangular parallelepiped ink jet heads 111vertical to the plate surface.

(Adjust Plate 113)

A description will be given of the adjust plate 113 in FIGS. 1 and 2with reference to FIGS. 4 and 5.

FIG. 4 shows a state in which the adjust plate 113 is mounted to each ofthe ink jet heads 111 for fixing each of the ink jet heads 111 underpositioned to the plate 112. The ink jet head 111 and the adjust plate113 are fixed in a fixing portion 126 of the former by an adhesiveagent, a resin, a screw, a rivet or the like in a state of adjustingsuch that a reference nozzle 123 of the former and a main reference hole124 of the latter are in a preset positional relationship, and thenozzle line 122 of the former is in parallel to a line obtained byconnecting the main reference hole 124 and a sub reference hole 125 ofthe latter. Since the reference nozzle 123 is very small, the adjustmentof the positional relationship is manually or automatically carried outby using a device capable of executing an enlarged observation such asan optical microscope, a CCD microscope, a laser microscope and thelike.

FIG. 5 shows the ink jet printer 101 in a state in which one ink jethead 111 among three ink jet heads 111 is detached from the plate 112.The ink jet head 111 is mounted and fixed to the plate 112 by fittingthe main reference hole 124 and the sub reference hole 125 of themounted adjust plate 113 to a main reference pin 127 and a sub referencepin 128 provided in the plate 112, respectively. As mentioned above, itis easy to attach and detach the ink jet head 111 and position the inkjet head 111 at a time of manufacturing and maintaining the line typeink jet head 102, by fixing the ink jet head 111 to the plate 112 by theadjust plate 113.

(Ink Tube 114 and Signal Cable 115)

The ink tube 114 in FIGS. 1 and 2 is a tube for supplying the ink to theink jet head 111, and the signal cable 115 is a cable for sending asignal to the ink jet head 111. The ink is an ink supplied from the inktank for making the ink jet head 111 to inject, and the signal is asignal (a drive pulse) sent from an ink jet head driver for driving theink jet head 111.

The ink tube 114 and the signal cable 115 are partly buried in the plate112. In other words, a portion between an ink tube 114A in a side of theink jet head 111 and an ink tube 114B in an opposite side to the ink jethead 111, and a portion between a signal cable 115A in a side of the inkjet head 111 and a signal cable 115B in an opposite side to the ink jethead 111 are buried in the plate 112. As mentioned above, since the inktube 114 and the signal cable 115 are buried in the plate 112, the inktube 114 and the signal cable 115 do not form an obstacle at a time ofmanufacturing and maintaining the line type ink jet head 102.

(Ink Tube Connector 116 and Signal Cable Connector 117)

The ink tube connector 116 in FIGS. 1 and 2 is a connector forconnecting the ink tubes 114 to each other, and the signal cableconnector 117 is a connector for connecting the signal cables 115 toeach other.

The ink tube connector 116 and the signal cable connector 117 arerespectively provided in a boundary between the ink tube 114A and thesignal cable 115A, and the plate 112. One ends 116A and 117A of the inktube connector 116 and the signal cable connector 117 are respectivelymounted to the ink tube 114A and the signal cable 115A, and another ends116B and 117B of the ink tube connector 116 and the signal cableconnector 117 are mounted to the plate 112. The ends 116B and 117B arerespectively connected to the ink tube 114B and the signal cable 115B.

If the ink tube connector 116 and the signal cable connector 117 aredetached at a time of attaching and detaching the ink jet head 111 andpositioning the ink jet head 111, ink tube 114 and the signal cable 115in the portion which is not buried in the plate 112 do not form theobstacle. As mentioned above, it is possible to easily attach and detachthe ink jet head 111 and easily position the ink jet head 111 at a timeof manufacturing and maintaining the line type ink jet head 102, byconnecting the ink tubes 114 to each other and connecting the signalcables 115 to each other by means of the ink tube connector 116 and thesignal cable connector 117.

(Ink Suction)

A description will be given here of an ink handling at a time ofdetaching the ink tube connector 116 with reference to FIG. 6. In orderto prevent the ink from dripping, it is necessary to previously drainthe ink at a time of detaching the ink tube connector 116. Accordingly,the structure is made, as shown in FIG. 6A, such that valves 129A and129B are respectively provided in the ink tube connectors 116A and 116B,whereby it is possible to shut the ink 104 passing as occasion demands.

In the case that the valve 129 is set to an “open state” as shown inFIG. 6B, the ink 104 can pass through, and in the case that the valve129 is set to a “closed state” as shown in FIG. 6C, the ink 104 can notpass through. The valve 129A and the valve 129B are respectively set tothe open state and the closed state, as shown in FIG. 6D, the ink 104 issucked from the nozzle of the ink jet head, and then, the ink tubeconnector 116 is detached, as shown in FIG. 6E. In this case, as shownin FIG. 6A, the valve 129C serving as an open valve is provided in theink tube connector 116B, and it is possible to smoothly execute thesuction of the ink 104 by setting the valve 129C to the “open state” soas to open to the atmospheric air, at a time of sucking the ink 104, asshown in FIG. 6D.

FIG. 6F shows a procedure of the ink suction. The print is stopped(S61), thereafter the valve 129B is set to the closed state (S62), andthe ink suction is executed (S63). At this time, the valve 129C is setto the open state (S64). Thereafter, the ink suction is stopped (S65),the valve 129 is set to the closed state (S66), and the ink tubeconnector 116 is detached (S67).

(Sub Ink Tank 118 and Ball Screw 119)

A description will be given of the sub ink tank 118 and the ball screw119 shown in FIGS. 1 and 2 with reference to FIGS. 7 to 12. In the casethat a trouble such as a clogging or the like is generated in the nozzleof the ink jet head, it is necessary to execute a “nozzle maintenance”such as sucking the ink from the nozzle of the ink jet head so as toremove foreign materials, bubbles, or the like. As mentioned below, at atime of executing the maintenance of the nozzle, it is necessary toinsert a maintenance unit for executing the maintenance of the nozzle toa lower portion of the plate. Accordingly, the plate is structured suchas to be freely moved in upward and downward directions, and the plate112 is moved upward at a time of maintaining the nozzle, as shown inFIG. 2. In the present embodiment, the plate 112 moves in the verticaldirection by the ball screw 119. In the case of using the other meansthan the ball screw 119, it is desirable to use a means such as an aircylinder, a hydraulic cylinder, and the like in which an operationaccompanies a low impact and a position repeatability is high.

FIG. 7 is a view for explaining the maintenance unit 701. In the ink jetprinter in accordance with the present embodiment, since the ink jethead is arranged on the paper-feeding path, it is hard to arrange themaintenance mechanism below the ink jet head.

Accordingly, as shown in FIG. 7A, the maintenance unit 701 is made tostand ready at a position apart from the plate 112 at a time ofprinting, and at a time of maintenance, the plate 112 is moved upward ina direction D3, the maintenance unit 701 is moved forward on a guiderail 702 in a direction D4, and the maintenance unit 701 is inserted tothe lower portion of the plate 112. The maintenance unit 701 is inserteduntil a cap 703 of the maintenance unit 701 comes just under the ink jethead 111.

Further, as shown in FIG. 7B, the plate 112 is moved downward in adirection D5, and the cap 703 of the maintenance unit 701 is closelycontacted with the ink jet head 111, as shown in FIG. 7C. The inner sideof the cap 703 is depressurized by discharging the air within the cap703 through a tube or the like communicating with the inner side of thecap 703, in this state, and the ink is sucked from the nozzle of the inkjet head 111.

FIG. 8 is a view for explaining the sub ink tank 118. In the ink jetprinter in accordance with the present embodiment, the structure is madesuch that the plate 112 can move in the upward and downward directions,as mentioned above. Accordingly, it is necessary to prevent the ink fromdripping from an ink injection surface 801 of the ink jet head 111, at atime when the plate 112 moved in the upward and downward directions.

Consequently, in the present embodiment, as shown in FIG. 8, the sub inktank 118 is fixed to the plate 112, and a height of an ink liquidsurface 802 in the sub ink tank 118 is controlled such that the inkinjection surface 801 of the ink jet head 111 is higher than the inkliquid surface 802 of the sub ink tank 118. An ink meniscus 804 of thenozzle 131 of the ink jet head 111 is maintained at a negative pressureon the basis of a water head difference W between the ink injectionsurface 801 and the ink liquid surface 802.

Further, it is possible to keep a state of preventing the bubbles frombeing sucked into the ink jet head 111 while the ink 104 is not drippedfrom the nozzle 131 and the ink meniscus 804 is slightly get sucked inthe ink jet head 111 from the nozzle 131, by controlling the height ofthe ink liquid surface 802 such that the water head difference W ismaintained at a preset value, in order to maintain the negative pressureat a proper value. As mentioned above, the ink meniscus 804 of the inkjet head 111 can be maintained in the stable state even when the movableplate 112 is moved, by fixing the sub ink tank 802 to the plate 112, andcontrolling the height of the ink liquid surface 802 of the sub ink tank118 such that the height of the ink liquid surface 802 of the sub inktank 118 is maintained at the set value with respect to the movableplate 112.

(Liquid Surface Control)

A description will be given here of a method of controlling the heightof the ink liquid surface 802 of the sub ink tank 118. The sub ink tank118 is provided with a liquid surface control sensor 901, as shown inFIG. 9. The liquid surface control sensor 901 is provided with a lowerlimit detecting portion 1001 and an upper limit-detecting portion 1002,as shown in FIG. 10A. Accordingly, as mentioned below, the set value ofthe height of the ink liquid surface 802 can be set to a “range from thelower limit value to the upper limit value”, and the height of the inkliquid surface 802 can be maintained at the set value. In this case, theliquid surface control sensor 901 may be provided with an ultrasonicsensor 1003, as shown in FIG. 10B.

In the case that the ink is consumed and the height of the ink liquidsurface 802 in the sub ink tank 118 reaches the lower limit value, thelower limit detecting portion 1001 detects the matter. When the matteris notified to the liquid surface control apparatus 902 from the liquidsurface control sensor 901, the liquid surface control apparatus 902sends an “operation signal” to a pump 903. When receiving the operationsignal, the pump 903 starts operating. Consequently, the ink reserved ina main ink tank 904 is supplied to the sub ink tank 118 through a filter905.

When the ink is supplied and the height of the ink liquid surface 802 inthe sub ink tank 118 reaches the upper limit value, the upper limitdetecting portion 1002 detects the matter. When the matter is notifiedto the liquid surface control apparatus 902 from the liquid surfacecontrol sensor 901, the liquid surface control apparatus 902 sends a“stop signal” to the pump 903. When receiving the stop signal, the pump903 stops.

In addition, a liquid surface control sensor 906 is provided in the mainink tank 904. When a height of an ink liquid surface 907 in the main inktank 904 reaches the lower limit value, the liquid surface controlsensor 906 informs the operator of the matter by means of lightening ofa patrol light 910 and a buzzer, at the same time of displaying an inkresidual amount on an indicator 909 of an ink residual amount displayapparatus 908.

FIG. 11 shows a procedure of the liquid surface control with respect tothe sub ink tank 118. As shown in FIG. 11, when the height of the inkliquid surface 802 in the sub ink tank 118 reaches the lower limit value(S111), the ink supply from the main ink tank 904 to the sub ink tank118 is started (S112), and the ink supply from the main ink tank 904 tothe sub ink tank 118 is continued (S113) until the height of the inkliquid surface 802 in the sub ink tank 118 reaches the upper limit value(S113).

FIG. 12 shows a procedure of the liquid surface control with respect tothe main ink tank 904. As shown in FIG. 12, the detection and thedisplay of the ink residual amount is continuously executed (S121), andthe patrol light 910 is turned on and the buzzer is sounded (S123), at atime when the height of the ink liquid surface 907 in the main ink tank904 reaches the lower limit value (S122).

The invention is not limited to the specifically disclosed embodiment,and various modified examples and embodiments can be considered withinthe claimed scope of the invention.

1. An ink jet printer comprising a line type ink jet head formed by aplurality of ink jet heads, characterized in that the plurality of inkjet heads are fixed to a plate, and an ink is injected to an inkreceiving subject from the plurality of ink jet heads in a state inwhich a plate surface of the plate and the ink receiving subject arefaced to each other; and a connector is provided adjacent to the ink jethead on the plate to connect tubes to each other and to connect cablesto each other, wherein the tubes are for supplying the ink to the inkjet head and the cables are for sending a signal to the ink jet head. 2.The ink jet printer according to claim 1, characterized in that the inkjet head is fixed to the plate by an adjust plate.
 3. The ink jetprinter according to claim 1, characterized in that a tube for supplyingthe ink to the ink jet head and/or a cable for sending a signal to theink jet head is buried in the plate.
 4. The ink jet printer according toclaim 1, characterized in that an ink tank for supplying the ink to theink jet head is fixed to the plate, and a height of an ink liquidsurface in the ink tank is controlled such that the height of the inkliquid surface in the ink tank is maintained at a set value with respectto the plate.
 5. The ink jet printer according to claim 1, furthercomprising a drive unit for lifting the plate from the position forprinting to execute a nozzle maintenance of the ink jet heads.
 6. Theink jet printer according to claim 5, further comprising a maintenanceunit having caps and being inserted to the position under the plate forcapping the ink jet heads.